I f***ed up my big bore and now my bike is garbage. - Page 3

2LZ · 04-19-2021, 12:57 PM

CC, please don't take this the wrong way, because i know that you have plenty of mechanical experience, but check to make sure the piston is installed in the correct orientation. I've been wrenching my whole life and have made worse mistakes.... It's worth a look.

franque · 04-19-2021, 03:44 PM

Quote:

Originally Posted by ChopperCharles

Verified timing like 30 times. It's timed correctly. Both the kit and the bike had stamped steel head gaskets.

Crankshaft was fine before this. Under 4000 miles.

Havent' checked compression, just going to pull it apart.

My guess is that of the two numbers for head bolt torque I found - 28 ft lbs and 50 Nm (37 ft lbs), the former is correct. I torqued to the latter, which may have over-compressed the head and base gaskets, reducing clearance and causing valve to piston contact.

Charles.

I have lots to say about this. Firstly, how are you so certain that you have valve to piston contact? If your hypothesis of over torqueing had any plausible causation in theoretical valve to piston contact, Zongshen has either some of the world's worst engineers working on the design, because the bolts/studs would/should always stretch before causing structural damage in the motor itself, or the metal itself is made of cheese, and I think in both cases, those are absurd assumptions.

Overtightening it at worst stretched the head bolts/studs; they wouldn't have the valves running so close to the piston in such a pedestrian application, because there's no benefit, this isn't a race motor, and there would need to be a far greater precision of assembly that doesn't come with a bike this cheap. It would also mean that valve float from revving the engine high would immediately destroy the valves, and trust me, there's a lot of leeway between the valves and piston, otherwise it wouldn't be marketed in 3rd world countries.

Did you actually turn the engine over before starting it to make sure there was nothing making undue noise, and no undue resistance?

The reason I keep railing on timing is because IF there was a manufacturing error in placing the timing marks on the cam(s) or flywheel, that could cause bent valves (but again, I suspect they're not), but if you suspected valves before with the last cylinder head, you should have done the above first, and also verified precise, physical timing with a piston stop and a degree wheel.

If you do a compression/leakdown test on the motor before disassembly, you would have an idea if the valves are actually bent, because you'd have a crapload of air constantly leaking in the cylinder that wouldn't go away, because the valves wouldn't be sealing. Taking it all the way down is most likely just chasing your tail, it would be better to have someone with OHC engine assembly experience take a look at it, if you're really concerned that it is completely destroyed, you're only likely to make things worse.

I assumed that with all of your CX500 experience and knowledge that you'd know better than to panic about everything, even if the design is completely different.

Overall, it seems like you're just looking for a reason to get rid of the bike, the panicked way you're talking about it makes it seem like you might just be better of selling it as-is to someone else for a fair price.

Edit: It could be the starter clutch lost one of the pieces that kept it from spinning backwards... I don't think it would start so easily with bent valves.

Edit 2: If it has an automatic decompressor, it could also be that it isn't properly set.

grumpyunk · 04-20-2021, 08:50 AM

I doubt there is piston:valve contact occurring. The engine would not start nor run with bent valves. There would be very little compression.
The noise, as well as computer speakers can convey, is not that 'impact' sound of metal to metal, but more something slopping around.
Could it be something as simple as a spacer left off of the cam or crank assembly allowing parts to shake around? Mental picture of the crank stackup assembly with a spacer/washer left out...
Is there a 'blow up' image of this model? When I put my CG back together, it was easy to get one of the gears installed incorrectly. It 'looked' right, but did not engage properly nor allow install of the next gear in the train. I don't know if this has gear or chain operation, but franque may be pointing in the right direction.
There was another post about a BBK install, on a Vader type engine, and the OP reported a similar type of noise. It would have been within the last 3-4 months.
I think there must be an assembly op that can be done in two ways... one of which results in noise, the other, not.
I cannot believe that the piston travel or TDC height is causing interference. The maker would not be able to sell the BBK if there was an interference condition built into the assembly.
tom

ChopperCharles · 04-20-2021, 09:30 AM

I'm not looking for a reason to get rid of the bike, I want to ride the goddamn thing. I've checked and verified the timing like 11 times now. It's spot on. Something is wrong and I won't know what it is until I take the engine apart again. I'm not panicking, I'm upset. This was supposed to be an easy fix.

Charles.

pyoungbl · 04-20-2021, 10:30 AM

Hi Charles, let's hope your problem is as simple as the automatic chain tensioner. I doubt that you have the timing so far off that metal bits are colliding in the cylinder. It's much more likely that the chain is slapping around. The engine would still start and run. You'd just have the extra slack running amok and making one hell of a noise. Pull the tensioner and see if it looks like it is taking up the tension correctly. As I recall, it's just two bolts securing it to the engine.

ChopperCharles · 04-20-2021, 10:49 AM

Tensioner is working properly. Timing is correct, for the millionth time.

Charles.

ChopperCharles · 04-28-2021, 11:06 PM

Okay, starting slow with the investigation and apart-taking.

How loose should the weight on the compression release be?

Here's a vid. Do you guys see anything wrong? If not, I'll take the head off next.

Charles.

grumpyunk · 04-29-2021, 06:55 AM

Unless the spring got damaged or distorted the CR appears to be working as it should. The flyweight that you moved on the outer side of the sprocket is moved by centrifugal force, moving the 'bump' on the cam lobe into the retracted position. When it is extended, it bumps the follower to allow some of the fuel:air mix in the chamber to vent, causing lower peak compression pressure. As the rpms go up, it moves outward, and the bump no longer nudges the follower and you get full compression.
The CR mechanism should 'sit still' and not do anything once you are rotating over cranking rpm. The spring is just there to move the 'bump' into position at low rpms, and centrifugal force should hold it in the fully retracted position with the engine running, with the arm being near the outer diameter of the sprocket.
The spring should have zero effect once the engine is running.
tom

ChopperCharles · 04-29-2021, 09:48 AM

Okay. Damn I was hoping it was something simple and I didn't have to pull the motor apart more.

Charles.

TxTaoRider · 04-29-2021, 09:58 AM

Did you check the piston to cylinder clearance before you assembled it? I've seen kits from Wiseco (and others) that had way too much and not enough clearence and with too much they'll make a bunch of racket and can rock enough to hit the head (not on hemi style heads but you get the idea). Too tight is much worse they'll quietly seize up and mess up the cylinder and piston.

ChopperCharles · 04-29-2021, 11:28 AM

No, I just installed the kit.

Charles.

bogieboy · 04-29-2021, 11:36 AM

Hey Charles, spin the motor over a little further and check the cam clearance to that screw boss right on the front side of the cam... the part of the cam lobe that goes over the compression release (between the sprocket and cam lobe) looks like it had made contact with something....

Working_ZS · 04-29-2021, 11:55 AM

Definitely do as bogieboy suggests; also be sure to illuminate it good with the light. It looks like something has worn on the base of the right exhaust cam lobe. You can see it at the 00:34 mark of the video.

grumpyunk · 04-30-2021, 10:14 AM

Can you post a picture of the bottom side of the cam follower assembly? The cam at the CR gadgetry looks as if it had conflict with something. Next to the lobe, and on the flat of the CR where one end of the spring sits, and on the edge of the cam boss where it bolts to the sprocket. .. All at about the same position (sort of facing in the same direction). Has to be something on the rocker/follower that intersects with the cam.
tom

ChopperCharles · 04-30-2021, 11:21 PM

So, there is pitting on the cam near the compression release. That was there when I took the bike apart the first time. It's not new, and I cant' see that it's causing the noise I experienced. The roller follower is still in good shape, and since the pitting isn't on the cam lobe I was inclined to just let it be.

Charles.

04-19-2021, 12:57 PM	#31
2LZ Join Date: Mar 2010 Location: Volcano, Ca Posts: 7,081	CC, please don't take this the wrong way, because i know that you have plenty of mechanical experience, but check to make sure the piston is installed in the correct orientation. I've been wrenching my whole life and have made worse mistakes.... It's worth a look. __________________ "Light a fire for a man, and you heat him for a day. Light a man on fire, and you heat him for the rest of his life." 2007 Suzuki DRZ400S (SM convert) 2009 Q Link XP 200 1967 BSA B25 250cc Starfire 2022 Royal Enfield Interceptor 650 2023 Royal Enfield Scram 411 1948 Royal Enfield Model G 350
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04-20-2021, 08:50 AM	#33
grumpyunk Join Date: Jul 2018 Location: nw of atlanta Posts: 169	I doubt there is piston:valve contact occurring. The engine would not start nor run with bent valves. There would be very little compression. The noise, as well as computer speakers can convey, is not that 'impact' sound of metal to metal, but more something slopping around. Could it be something as simple as a spacer left off of the cam or crank assembly allowing parts to shake around? Mental picture of the crank stackup assembly with a spacer/washer left out... Is there a 'blow up' image of this model? When I put my CG back together, it was easy to get one of the gears installed incorrectly. It 'looked' right, but did not engage properly nor allow install of the next gear in the train. I don't know if this has gear or chain operation, but franque may be pointing in the right direction. There was another post about a BBK install, on a Vader type engine, and the OP reported a similar type of noise. It would have been within the last 3-4 months. I think there must be an assembly op that can be done in two ways... one of which results in noise, the other, not. I cannot believe that the piston travel or TDC height is causing interference. The maker would not be able to sell the BBK if there was an interference condition built into the assembly. tom __________________ vertical and above ground - my daily goal
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04-29-2021, 06:55 AM	#38
grumpyunk Join Date: Jul 2018 Location: nw of atlanta Posts: 169	Unless the spring got damaged or distorted the CR appears to be working as it should. The flyweight that you moved on the outer side of the sprocket is moved by centrifugal force, moving the 'bump' on the cam lobe into the retracted position. When it is extended, it bumps the follower to allow some of the fuel:air mix in the chamber to vent, causing lower peak compression pressure. As the rpms go up, it moves outward, and the bump no longer nudges the follower and you get full compression. The CR mechanism should 'sit still' and not do anything once you are rotating over cranking rpm. The spring is just there to move the 'bump' into position at low rpms, and centrifugal force should hold it in the fully retracted position with the engine running, with the arm being near the outer diameter of the sprocket. The spring should have zero effect once the engine is running. tom __________________ vertical and above ground - my daily goal Last edited by grumpyunk; 04-30-2021 at 10:14 AM. Reason: spell CT or CR
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04-29-2021, 09:58 AM	#40
TxTaoRider Join Date: Oct 2020 Location: Flower Mound Texas Posts: 904	Did you check the piston to cylinder clearance before you assembled it? I've seen kits from Wiseco (and others) that had way too much and not enough clearence and with too much they'll make a bunch of racket and can rock enough to hit the head (not on hemi style heads but you get the idea). Too tight is much worse they'll quietly seize up and mess up the cylinder and piston. __________________ 2021 Tao Tbr7 - "Lucille" Mods so far- Brozz swingarm, 21" front rim (Bridgestone Tw302 rear/Dunlop D606 front tires), Digital gauge cluster, pz30b pumper carb, after market hand guards, aftermarket brake and clutch levers, round fold away mirrors, Fly handlebars shortened slightly, 13t front sprocket 2009 Q-link Legacy 250 1982 Suzuki GS1100ES - "Jolene"
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04-30-2021, 10:14 AM	#44
grumpyunk Join Date: Jul 2018 Location: nw of atlanta Posts: 169	Can you post a picture of the bottom side of the cam follower assembly? The cam at the CR gadgetry looks as if it had conflict with something. Next to the lobe, and on the flat of the CR where one end of the spring sits, and on the edge of the cam boss where it bolts to the sprocket. .. All at about the same position (sort of facing in the same direction). Has to be something on the rocker/follower that intersects with the cam. tom __________________ vertical and above ground - my daily goal
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04-20-2021, 09:30 AM	#34
ChopperCharles Join Date: Feb 2018 Location: RDU, NC Posts: 677	I'm not looking for a reason to get rid of the bike, I want to ride the goddamn thing. I've checked and verified the timing like 11 times now. It's spot on. Something is wrong and I won't know what it is until I take the engine apart again. I'm not panicking, I'm upset. This was supposed to be an easy fix. Charles.
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04-20-2021, 10:30 AM	#35
pyoungbl Join Date: Feb 2016 Location: Portsmouth, Virginia, USA Posts: 632	Hi Charles, let's hope your problem is as simple as the automatic chain tensioner. I doubt that you have the timing so far off that metal bits are colliding in the cylinder. It's much more likely that the chain is slapping around. The engine would still start and run. You'd just have the extra slack running amok and making one hell of a noise. Pull the tensioner and see if it looks like it is taking up the tension correctly. As I recall, it's just two bolts securing it to the engine.
	1

04-20-2021, 10:49 AM	#36
ChopperCharles Join Date: Feb 2018 Location: RDU, NC Posts: 677	Tensioner is working properly. Timing is correct, for the millionth time. Charles.
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04-28-2021, 11:06 PM	#37
ChopperCharles Join Date: Feb 2018 Location: RDU, NC Posts: 677	Okay, starting slow with the investigation and apart-taking. How loose should the weight on the compression release be? Here's a vid. Do you guys see anything wrong? If not, I'll take the head off next. Charles.
	1

04-29-2021, 09:48 AM	#39
ChopperCharles Join Date: Feb 2018 Location: RDU, NC Posts: 677	Okay. Damn I was hoping it was something simple and I didn't have to pull the motor apart more. Charles.
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04-29-2021, 11:28 AM	#41
ChopperCharles Join Date: Feb 2018 Location: RDU, NC Posts: 677	No, I just installed the kit. Charles.
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04-29-2021, 11:36 AM	#42
bogieboy Join Date: May 2013 Location: finger lakes NY Posts: 2,045	Hey Charles, spin the motor over a little further and check the cam clearance to that screw boss right on the front side of the cam... the part of the cam lobe that goes over the compression release (between the sprocket and cam lobe) looks like it had made contact with something....
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04-29-2021, 11:55 AM	#43
Working_ZS Join Date: Aug 2016 Posts: 365	Definitely do as bogieboy suggests; also be sure to illuminate it good with the light. It looks like something has worn on the base of the right exhaust cam lobe. You can see it at the 00:34 mark of the video.
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04-30-2021, 11:21 PM	#45
ChopperCharles Join Date: Feb 2018 Location: RDU, NC Posts: 677	So, there is pitting on the cam near the compression release. That was there when I took the bike apart the first time. It's not new, and I cant' see that it's causing the noise I experienced. The roller follower is still in good shape, and since the pitting isn't on the cam lobe I was inclined to just let it be. Charles.
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